A. Field of the Invention
The device of the present invention relates generally to a new and improved connector for high tensile load attachment to an elongated element, such as a resin bonded, glass reinforced rod, to a new and improved method for maintaining a high tensile load attachment to an elongated element, to a new and improved suspension insulator, to a new and improved method for manufacturing suspension insulators, to a new and improved sucker rod and to a new and improved method for actuating a remotely located pump.
B. Description of the Prior art
There is a need unfulfilled by prior art devices for low cost elongated rods and end fittings or connectors for these rods capable of carrying high tensile loads. In many geographical locations, there are wide variations in both temperature and environmental conditions. In these locations, prior art connectors that are capable of carrying high tensile loads are technically or economically undesirable.
A specific example of a common connector of this type is the end fitting used in rod type suspension insulators to support or suspend high voltage power cables from transmission towers. Due to the very high tensile loads and large temperature variations, these prior art end fittings tend to exert excessive shear stresses on the rod or suffer a change in the physical characteristics of the materials that form the end fittings.
One type of prior art fitting employs a cylindrical metal sleeve placed between compression dies and compressed about the end of a rod. An example of this type of prior art fitting is disclosed in U.S. Pat. No. 3,192,622. Such fittings tend to be excessively long and to creep upon being subjected to high tensile loads and high temperatures.
Another example of a typical prior art fitting is the fitting employing a metal wedge set forth in U.S. Pat. No. 3,698,749. This type of fitting is costly to produce and tends either to spot load the rod or to lose its shear strength at the interface between the wedge and the rod.
Other common prior art end fittings are expensive to manufacture and require large amounts of potting material between the end fitting and the rod, thus making the suspension insulator more susceptible to failure upon being exposed to temperature and environmental variations. These characteristics reduce the capability of prior art suspension insulators to achieve high tensile loading.
Furthermore, there is a need for low cost, lightweight, rigid rods and interconnections between adjacent rods for actuating remotely located pumps, such as oil well pumps. When the oil pressure in an oil field has fallen to a point where the oil is not naturally lifted to the surface, artificial means must be used to lift the oil to the surface. One artificial means is an oil well pump placed at the bottom of the oil well and actuated by a plurality or string of rods, commonly referred to as a sucker rod string. A typical sucker rod string includes a plurality of steel rods having lengths of between 25 and 30 feet and diameters of 1/2, 5/8, 3/4, 7/8, 1 or 11/2 inches interconnected by threaded couplings. A typical pumping unit including a typical sucker rod string is fully disclosed and discussed in a reference book entitled PRIMER OF OIL AND GAS PRODUCTION (1971), published by the American Petroleum Institute. See particularly Chapter 5, pages 23-26. In addition, the special problems encountered in this method of oil production are discussed in Chapter 10.
Typical steel sucker rods must be replaced at rather frequent intervals due to corrosion. Many attempts have been made to reduce corrosion or the effects of corrosion. For example, plastic coatings have been developed for application to metal surfaces to protect the metal surfaces from corrosion. In many low pressure systems, plastic pipe is being used as a substitute for steel pipe to reduce corrosion problems. However, the plastic pipe typically does not have the same strength as the metal pipe. For all of the above reasons, a need exists for corrosion resistant, high tensile strength sucker rod strings for use in pumping oil to the surface.